Ah okay, I see. I was using NA as my example because it's what I know the most about, and I think it has the most obvious suburban form. There are other countries around the world that exhibit similar patterns.

My point about single-family being cheapest to build is indeed a US political problem, because through law/taxation we have incentivized it to be. By cheapest to build, I mean including municipal development charges and the land cost. The external costs of these developments (increased carbon emissions, less efficient land use) are not being paid for by the developer, so taxpayers/local governments are not being forced to pay for that burden.